An example biome in 1.16.2

ExampleBiome1162.java

package voronoiaoc.byg.common.biomes.biomes;

import net.minecraft.entity.EntityType;
import net.minecraft.entity.SpawnGroup;
import net.minecraft.sound.BiomeMoodSound;
import net.minecraft.world.biome.*;
import net.minecraft.world.gen.feature.DefaultBiomeFeatures;
import net.minecraft.world.gen.surfacebuilder.ConfiguredSurfaceBuilder;
import net.minecraft.world.gen.surfacebuilder.SurfaceBuilder;
import voronoiaoc.byg.common.biomes.BiomeHelper;
import voronoiaoc.byg.common.biomes.BiomeTools;
import voronoiaoc.byg.common.world.feature.biomefeatures.BYGFeatures;
import voronoiaoc.byg.common.world.feature.biomefeatures.BYGTreeFeatures;
import voronoiaoc.byg.core.byglists.BYGBiomeList;

import javax.annotation.Nullable;
import java.util.Optional;
import java.util.Random;

public class AncientForest extends Biome implements BiomeTools {
    static final ConfiguredSurfaceBuilder<?> SURFACE_BUILDER = new ConfiguredSurfaceBuilder<>(SurfaceBuilder.DEFAULT, SurfaceBuilder.GRASS_CONFIG);
    static final Precipitation PRECIPATATION = Precipitation.RAIN;
    static final Category CATEGORY = Category.FOREST;
    static final float DEPTH = 0.2F;
    static final float SCALE = 0.05F;
    static final float TEMPERATURE = 0.8F;
    static final float DOWNFALL = 0.8F;
    static final int WATER_COLOR = 4159204;
    static final int WATER_FOG_COLOR = 329011;
    static final String PARENT = null;
    static final Weather WEATHER = new Weather(PRECIPATATION, TEMPERATURE, TemperatureModifier.NONE, DOWNFALL);
    static final SpawnSettings.class_5496 SPAWN_SETTINGS = new SpawnSettings.class_5496();
    static final GenerationSettings.class_5495 GENERATION_SETTINGS = (new GenerationSettings.class_5495()).method_30996(SURFACE_BUILDER);

    public AncientForest() {
        super(WEATHER, CATEGORY, DEPTH, SCALE, (new BiomeEffects.Builder()).waterColor(WATER_COLOR).waterFogColor(WATER_FOG_COLOR).fogColor(12638463).skyColor(BiomeHelper.calcSkyColor(0.8F)).moodSound(BiomeMoodSound.CAVE).build(), GENERATION_SETTINGS.method_30987(), SPAWN_SETTINGS.method_31007(), Optional.ofNullable(PARENT));
    }

    @Nullable
    @Override
    public Biome getHill() {
        BYGBiomeList.FLOWERING_ANCIENT_FOREST;
    }

    @Override
    public Biome getRiver() {
        return Biomes.RIVER;
    }

    static {
        DefaultBiomeFeatures.addDefaultUndergroundStructures(GENERATION_SETTINGS);
        BYGTreeFeatures.addAncientTrees(GENERATION_SETTINGS);
        BYGTreeFeatures.addMeadowTrees(GENERATION_SETTINGS);
        BYGTreeFeatures.addShrubs(GENERATION_SETTINGS);
        BYGTreeFeatures.addHugeMushrooms(GENERATION_SETTINGS);
        DefaultBiomeFeatures.addLandCarvers(GENERATION_SETTINGS);
        DefaultBiomeFeatures.addDungeons(GENERATION_SETTINGS);
        DefaultBiomeFeatures.addMineables(GENERATION_SETTINGS);
        DefaultBiomeFeatures.addDefaultOres(GENERATION_SETTINGS);
        DefaultBiomeFeatures.addDefaultDisks(GENERATION_SETTINGS);
        DefaultBiomeFeatures.addDefaultMushrooms(GENERATION_SETTINGS);
        DefaultBiomeFeatures.addDefaultVegetation(GENERATION_SETTINGS);
        DefaultBiomeFeatures.addFrozenTopLayer(GENERATION_SETTINGS);
        BYGFeatures.addGrass(GENERATION_SETTINGS);
        BYGFeatures.addLolliPop(GENERATION_SETTINGS);
        BYGFeatures.addBYGMushrooms(GENERATION_SETTINGS);
        BYGFeatures.addFairyslipper(GENERATION_SETTINGS);
        BYGFeatures.addFairyslipper(GENERATION_SETTINGS);
        BYGFeatures.addBlackRose(GENERATION_SETTINGS);
        BYGFeatures.addRose(GENERATION_SETTINGS);
        BYGFeatures.addLushBlueberries(GENERATION_SETTINGS);
        SPAWN_SETTINGS.method_31011(SpawnGroup.CREATURE, new SpawnSettings.SpawnEntry(EntityType.PIG, 10, 4, 4));
        SPAWN_SETTINGS.method_31011(SpawnGroup.CREATURE, new SpawnSettings.SpawnEntry(EntityType.WOLF, 8, 4, 4));
        SPAWN_SETTINGS.method_31011(SpawnGroup.CREATURE, new SpawnSettings.SpawnEntry(EntityType.RABBIT, 4, 2, 3));
        SPAWN_SETTINGS.method_31011(SpawnGroup.CREATURE, new SpawnSettings.SpawnEntry(EntityType.FOX, 8, 2, 4));
        SPAWN_SETTINGS.method_31011(SpawnGroup.AMBIENT, new SpawnSettings.SpawnEntry(EntityType.BAT, 10, 8, 8));
        SPAWN_SETTINGS.method_31011(SpawnGroup.MONSTER, new SpawnSettings.SpawnEntry(EntityType.CAVE_SPIDER, 100, 4, 4));
        SPAWN_SETTINGS.method_31011(SpawnGroup.MONSTER, new SpawnSettings.SpawnEntry(EntityType.SLIME, 100, 4, 4));
        SPAWN_SETTINGS.method_31011(SpawnGroup.MONSTER, new SpawnSettings.SpawnEntry(EntityType.ENDERMAN, 10, 1, 4));
        SPAWN_SETTINGS.method_31011(SpawnGroup.MONSTER, new SpawnSettings.SpawnEntry(EntityType.WITCH, 5, 1, 1));
    }
}